将（Sinatra）Ruby值传递给Javascript

Question

So, i'm making a subscribe form.

Jquery

    $("<div id='dialog' title='Subscribe!'> <form id='subscribe_form' method='POST' action='/user/subscribe'>" +
        "<input type='text' name='subscribe_email' id='email' placeholder='Email Address'> <br/>" +
        "<button id='submit_subscribe_form'>Submit</button></p><p id='ruby_bool'></p></form>" +
        "</div>").appendTo($("#subscribe"));

When this form is submitted, it sends an ajax call to a Ruby Sinatra listener (sorry if I'm not using the right terminology, haven't really been taught Sinatra, just shown how to use it)

 $('form').submit(function(){
        $.ajax({
            type: "POST",
            url: "/user/subscribe",
            data: $('form').serialize(),
            success: function()
            {

Ruby Code

 post "/user/subscribe" do

user_Information = EmailList.new

if params[:subscribe_email] =~ /^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/
  user_Information.email = params[:subscribe_email]
  puts user_Information.save
  @email_validation_result = "True"
else
  @email_validation_result = "False"
end

puts @email_validation_result

(Yes i know i shouldn't use regex, but the engines i could find were for PHP) I want to use the @email validation result so i can know what to put in my success: call in my ajax. Problem is, JavaScript doesn't allow Ruby Injection (according to my god knows how many hours of research) and i cant update a div on the web page that contains that variable async. I want to do this all async, so there is no refreshing of the entire page whatsoever. (If it's not possible otherwise i will concede, but i highly doubt that). I tried to put the div on another page and use the JQuery .load() function, but .erb files aren't recognizable. Out of ideas and nearly out of sanity. Thanks!

Answer 1

JavaScript:

$.post( '/user/subscribe', $('form').serialize(), function(data){
  // Do whatever you want with the response from the server here
  // data is a JavaScript object.
}, 'json');

Ruby/Sinatra:

require 'json' # just for a convenient way to serialize

post '/user/subscribe' do
  # process the params however you want

  content_type 'application/json'
  { :ok => @is_ok }.to_json
end

Without the JSON library you could end your method with just some valid JSON markup, like:

%Q[ { "ok":#{@is_ok} } ]

JavaScript/AJAX will post to the server, the matching Sinatra route will process the request, and the string result of that method ( not done via puts ) will be sent as the response to the method. The jQuery AJAX handler will receive it, parse it as JSON and invoke your callback function, passing the JavaScript object it created as the parameter. And then you can modify your HTML DOM as desired, client side.